#include <stdio.h>

//https://www.nowcoder.com/practice/586b114f52034688879342ba45779081?tpId=290&tags=&title=&difficulty=0&judgeStatus=0&rp=0&sourceUrl=%2Fexam%2Foj%2Fta%3FtpId%3D290

int main() {
    int n = 0;
    int sum = 0;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
        sum += i * (n - i + 1);
    }
    printf("%d", sum);
    return 0;
}
